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LeetCode 720 — find the longest word in a dictionary that can be built one character at a time, with each prefix also in the dictionary. Trie + BFS gives lex-smallest tie-breaking for free.
LeetCode 336 — find every pair (i,j) such that words[i] + words[j] is a palindrome. The trie solution stores reversed words and tags palindrome-suffix indices, enabling O((N times K^2)) lookup.
LeetCode 1032 — design a class that returns true whenever the suffix of a streamed character sequence matches any dictionary word. Solved with a reverse trie and a bounded sliding buffer in O(W) per query.
LeetCode 745 — design a structure that returns the highest-indexed word matching a given prefix and suffix. The combined-key trie inserts every (suffix#word) variant, turning a 2D query into a 1D trie walk.
LeetCode 2416 — for each word, sum the scores of all its non-empty prefixes where score = number of words sharing that prefix. The counted trie pattern aggregates O(N times L) work into O(N times L) trie nodes with a count counter.